SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION - Market-based options vesting prices (Details)	Dec. 31, 2016 $ / shares shares
Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	129,513
Market-based options, weighted average share price (in dollars per share) | $ / shares	$ 50.32
Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	106,518
Market-based options, weighted average share price (in dollars per share) | $ / shares	$ 48.13
$40.01 — $50.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	40.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 50.00
$40.01 — $50.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	14,500
$40.01 — $50.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$50.01 — $60.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 50.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 60.00
$50.01 — $60.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	47,129
$50.01 — $60.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	16,483
$60.01 — $70.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 60.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 70.00
$60.01 — $70.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	17,884
$60.01 — $70.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	6,250
$70.01 — $80.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 70.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 80.00
$70.01 — $80.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$70.01 — $80.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	1,000
$80.01 — $90.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 80.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 90.00
$80.01 — $90.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$80.01 — $90.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	25,467
$90.01 — $100.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 90.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 100.00
$90.01 — $100.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	2,500
$90.01 — $100.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	8,943
$140.01 — $150.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 140.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 150.00
$140.01 — $150.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	12,500
$140.01 — $150.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	1,250
$170.01 — $180.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 170.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 180.00
$170.01 — $180.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	12,500
$170.01 — $180.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$180.01 — $190.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 180.01
Market-based options, vesting price, high end of range (in dollars per share) | $ / shares	$ 190.00
$180.01 — $190.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	0
$180.01 — $190.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	23,375
Over $190.00
Market prices for market performance options to vest
Market-based options, vesting price, low end of range (in dollars per share) | $ / shares	$ 190.01
Over $190.00 | Ordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	22,500
Over $190.00 | Extraordinary performance grants
Market prices for market performance options to vest
Market-based options, options expected to vest (in shares)	23,750